Association of antimicrobial perioperative prophylaxis with cefuroxime plus metronidazole or amoxicillin/clavulanic acid and surgical site infections in colorectal surgery

Table 3 Risk factors for SSI

Risk factor	Crude odds ratio [95% CI]	P value	Adjusted odds ratio [95% CI]	p Value
Amoxicillin/clavulanic acid	1.45 [1.21, 1.75]	< 0.001	1.49 [1.24, 1.78]	< 0.001
Age (10 year steps)	1.03 [1.00, 1.06]	0.05	0.96 [0.93, 0.98]	0.003
Female sex	0.67 [0.62, 0.73]	< 0.001	0.75 [0.69, 0.81]	< 0.001
ASA score > 2	1.67 [1.57, 1.79]	< 0.001	1.44 [1.33, 1.56]	< 0.001
Operation duration (per 30 min)	1.08 [1.06, 1.10]	< 0.001	1.08 [1.06, 1.09]	< 0.001
Antibiotic prophylaxis (in 30 min steps prior to incision)*	0.94 [0.89, 0.99]	0.03	0.95 [0.91, 0.99]	0.02
Duration of surgery > 75th percentile	1.38 [1.24, 1.53]	< 0.001	ns
Elective surgery	0.59 [0.52, 0.66]	< 0.001	0.75 [0.66, 0.85]	< 0.001
Laparoscopic interventions	0.53 [0.47, 0.59]	< 0.001	0.60 [0.54, 0.67]	< 0.001
Rectal surgery	1.09 [0.75, 1.57]	0.7	ns
Hospital size (N beds)
< 200	1 (reference)
200–499	1.12 [0.85, 1.46]	0.43	ns
500+	1.30 [1.07, 1.58]	0.009	ns
Re-operation**	4.85 [3.82, 6.15]	< 0.001	4.31 [3.37, 5.52]	< 0.001

*Of the first antibiotic administered (if in combination)
**For a non-infectious complication during the follow-up period
CI, confidence interval; ASA, American Society of Anesthesiology; ns, not significant (not retained in the multivariable model)

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